Coaxial prime focus feeds for paraboloidal reflectors

A TE11 - TM11 dual mode coaxial feed for use in prime focus paraboloidal antenna systems is investigated. The scattering matrix parameters of the internal bifurcation junction was determined by the residue calculus technique. The scattering parameters and radiation fields of the aperture were found from the Weinstein solution. The optimum modeing ratio for minimum cross-polarization was determined along with the corresponding optimum feed dimensions. A peak cross-polarization level of -58 dB is predicted. The frequency characteristics were also investigated and a bandwidth of 5% is predicted over which the cross-polarization remains below -30 dB, the input VSWR is below 1.15, and the phase error is less than 10 deg. Theoretical radiation patterns and efficiency curves for a paraboloidal reflector illuminated by this feed were computed. The predicted sidelobe level is below -30 dB and aperture efficiencies greater than 70% are possible. Experimental results are also presented that substantiates the theoretical results. In addition, experimental results for a 'short-cup' coaxial feed are given. The report includes extensive design data for the dual-mode feed along with performance curves showing cross-polarization as a function of feed parameters. The feed is useful for low-cost ground based receiving antennas for use in direct television satellite broadcasting service

Microscopic Observations of Voids in Anodic Oxide Films on Aluminum

The relationship was explored between nanoscale voids in anodic aluminum oxide films and the surface condition of aluminum samples prior to anodizing. Transmission electron microscopy (TEM) detected voids on the order of 10 nm in anodic films. Atomic force microscopy (AFM) of these films, obtained after partial oxide dissolution, revealed surface cavities; comparison of TEM and AFM suggested that the cavities were the oxide voids. AFM images after variable extents of oxide dissolution showed that the voids were distributed evenly through the inner 60% of the film thickness, indicating that they were formed at the metal-oxide interface during film growth. Both AFM and TEM showed that the void concentration in the film was sensitive to the extent of dissolution of the aluminum samples in NaOH prior to anodizing. Positron annihilation spectroscopy had previously detected voids in samples without anodic films, located in the metal near the oxide-metal interface; the quantity of these interfacial voids was controlled by NaOH dissolution. The void concentration in the inner part of the anodic films was proportional to the quantity of these pre-existing interfacial voids. It was inferred that the oxide voids were formed by incorporation, during anodizing, of interfacial metal voids into the oxide film. The uniform concentration of oxide voids in the inner film suggested that interfacial metal voids formed continuously during anodizing and that metal voids were generated repeatedly at specific interfacial sites during film growth

Attractive Hubbard Model on a Honeycomb Lattice

We study the attractive fermionic Hubbard model on a honeycomb lattice using determinantal quantum Monte Carlo simulations. By increasing the interaction strength U (relative to the hopping parameter t) at half-filling and zero temperature, the system undergoes a quantum phase transition at 5.0 < U_c/t < 5.1 from a semi-metal to a phase displaying simultaneously superfluid behavior and density order. Doping away from half-filling, and increasing the interaction strength at finite but low temperature T, the system always appears to be a superfluid exhibiting a crossover between a BCS and a molecular regime. These different regimes are analyzed by studying the spectral function. The formation of pairs and the emergence of phase coherence throughout the sample are studied as U is increased and T is lowered

Cellular mechanisms of prostaglandin E2 and vasopressin interactions in the collecting duct

As the final segment of the nephron, the collecting duct is the ultimate regulator of renal salt and water excretion. Balance between intake and renal excretion of salt and water is fine-tuned by the action of several hormones targeted to the collecting duct. Vasopressin is, perhaps, the prototypical example of such a hormone. As total body water decreases and plasma osmolality rises, vasopressin secretion from the posterior pituitary increases [1]. Picomolar concentrations of circulating vasopressin lead to increased water permeability of the apical membrane of the collecting duct cell, resulting in increased water reabsorption and increased total body water [2,3]. There is abundant evidence demonstrating that vasopressin's effect on water reabsorption in the collecting duct is mediated through the classic second messenger, cAMP [3]. V2 selective receptors are linked via a G protein, to stimulation of plasma membrane adenylyl cyclase, resulting in increased cell cyclic AMP levels [4, 5]. The increased cyclic AMP then leads to augmented water permeability of the apical membrane [6, 7].As one might expect with such an important biologic process, other hormones and autocoids provide a counter-regulatory influence to modulate vasopressin mediated increases in osmotic water permeability. There is good evidence that the arachadonic acid metabolite, prostaglandin E2 (PGE2) plays a critical physiologic and pathophysiologic role in inhibiting vasopressin action in the collecting duct [8, 9]. Not only is the collecting duct the major renal site of synthesis for this cyclo-oxygenase product of arachidonic acid but PGE2 production is stimulated by vasopressin itself [10–12]. PGE2 infusion significantly blunts water reabsorption and cycloxygenase inhibition augments vasopressin antidiuresis [9, 13]. Thus, there is good evidence that the autocoid PGE2 plays an important role in regulating vasopressin-stimulated osmotic water flow

Bilingualism Is Associated with a Delayed Onset of Dementia but Not with a Lower Risk of Developing it: a Systematic Review with Meta-Analyses.

Some studies have linked bilingualism with a later onset of dementia, Alzheimer's disease (AD), and mild cognitive impairment (MCI). Not all studies have observed such relationships, however. Differences in study outcomes may be due to methodological limitations and the presence of confounding factors within studies such as immigration status and level of education. We conducted the first systematic review with meta-analysis combining cross-sectional studies to explore if bilingualism might delay symptom onset and diagnosis of dementia, AD, and MCI. Primary outcomes included the age of symptom onset, the age at diagnosis of MCI or dementia, and the risk of developing MCI or dementia. A secondary outcome included the degree of disease severity at dementia diagnosis. There was no difference in the age of MCI diagnosis between monolinguals and bilinguals [mean difference: 3.2; 95% confidence intervals (CI): -3.4, 9.7]. Bilinguals vs. monolinguals reported experiencing AD symptoms 4.7 years (95% CI: 3.3, 6.1) later. Bilinguals vs. monolinguals were diagnosed with dementia 3.3 years (95% CI: 1.7, 4.9) later. Here, 95% prediction intervals showed a large dispersion of effect sizes (-1.9 to 8.5). We investigated this dispersion with a subgroup meta-analysis comparing studies that had recruited participants with dementia to studies that had recruited participants with AD on the age of dementia and AD diagnosis between mono- and bilinguals. Results showed that bilinguals vs. monolinguals were 1.9 years (95% CI: -0.9, 4.7) and 4.2 (95% CI: 2.0, 6.4) older than monolinguals at the time of dementia and AD diagnosis, respectively. The mean difference between the two subgroups was not significant. There was no significant risk reduction (odds ratio: 0.89; 95% CI: 0.68-1.16) in developing dementia among bilinguals vs. monolinguals. Also, there was no significant difference (Hedges' g = 0.05; 95% CI: -0.13, 0.24) in disease severity at dementia diagnosis between bilinguals and monolinguals, despite bilinguals being significantly older. The majority of studies had adjusted for level of education suggesting that education might not have played a role in the observed delay in dementia among bilinguals vs. monolinguals. Although findings indicated that bilingualism was on average related to a delayed onset of dementia, the magnitude of this relationship varied across different settings. This variation may be due to unexplained heterogeneity and different sources of bias in the included studies. Registration: PROSPERO CRD42015019100

Assessing the impact of a national clinical guideline for the management of chronic pain on opioid prescribing rates:a controlled interrupted time series analysis

Background: Opioids can be effective analgesics, but long-term use may be associated with harms. In 2013, the first national, comprehensive, evidence-based pain management guideline was published, from the Scottish Intercollegiate Guideline Network (SIGN 136: Management of Chronic Pain) with key recommendations on analgesic prescribing. This study aimed to examine the potential impact on national opioid prescribing rates in Scotland. Methods: Trends in national and regional community opioid prescribing data for Scotland were analysed from quarter one (Q1) 2005 to Q2 2020. Interrupted time series regression examined the association of SIGN 136 publication with prescribing rates for opioid-containing drugs. Gabapentinoid prescribing was used as a comparison drug. Results: After a positive prescribing trend pre-publication, the timing of SIGN 136 publication was associated with a negative change in the trend of opioid prescribing rates (−2.82 items per 1000 population per quarter [PTPPQ]; P < 0.01). By Q2 2020, the relative reduction in the opioid prescribing rate was −20.67% (95% CI: −23.61, −17.76). This persisted after correcting for gabapentinoid prescribing and was mainly driven by the reduction in weak opioids, whereas strong opioid prescribing rates continued to rise. Gabapentinoid prescribing showed a significant rise in level (8.00 items per 1000 population; P = 0.01) and trend (0.27 items PTPPQ; P = 0.01) following SIGN 136 publication. Conclusions: The publication of SIGN 136 was associated with a reduction in opioid prescribing rates. This suggests that changes in clinical policy through evidence-based national clinical guidelines may affect community opioid prescribing, though this may be partially replaced by gabapentinoids, and other factors may also contribute

Psychosocial Stress and Prostate Cancer: A Theoretical Model

African-American men are more likely to develop and die from prostate cancer than are European-American men; yet, factors responsible for the racial disparity in incidence and mortality have not been elucidated. Socioeconomic disadvantage can lead to psychosocial stress and may be linked to negative lifestyle behaviors. Regardless of socioeconomic position, African-American men routinely experience racism-induced stress. We propose a theoretical framework for an association between psychosocial stress and prostate cancer. With the context of history and culture, we further propose that psychosocial stress may partially explain the variable incidence of prostate cancer between these diverse groups. Psychosocial stress may negatively impact teh immune system leaving the individual susceptible to malingnancies. Behavioral responses to psychosocial stress are amenable to change. If psychosocial stress is found to negatively impact prostate cancer risk, interventions may be designed to modify reactions to environmental demands